The present invention relates to a disk playback system that is used in a CD-ROM playback apparatus or the like that reads out information recorded on a disk to transfer to an external device.
Taking a CD-ROM playback apparatus as an example, we describe a conventional kind of disk playback system. The CD-ROM playback apparatus receives a command from an external device such as a personal computer to search for a desired position and reads out desired data from the data recorded on a disk to transfer to an external device. An audio CD (compact disk) and a CD-ROM disk are recorded with a constant linear velocity (CLV) and supposed to be played back at one time the velocity.
In recent years, as personal computers increase their speed, high-speed readout and high-speed access are demanded for CD-ROM playback apparatus as a peripheral equipment of computers. In order to satisfy such demands, CD-ROM playback apparatuses that perform a constant high-speed readout at 2 times or 4 times the CLV or the like during playback time of a CD-ROM disk are now on the market. However, in order to raise search speed with constant high-speed readout at 2 times or 4 times the CLV or the like, loads on the disk motor that drives the disk become exceedingly large, so that there has been a problem that a large-sized disk motor at high cost is required.
Therefore, there are sold at a market CD-ROM playback D apparatuses that employ the CAV playback method that plays back at CAV (constant angular velocity) a disk that has been recorded at CLV, the wide-range CLV playback method that is CLV but has a very wide playback range and can perform high-speed searches and constant high-speed playbacks, or the PCAV (partial CAV) playback method that is a combination of the CAV playback method and the wide-range CLV playback method. CD-ROM playback apparatuses that employ these methods all realize high-speed searches by lightening the loads on their disk motors to use low-priced and compact disk motors.
Now, in a CD-ROM playback system that employs the above CAV playback method, wide-range CLV playback method, PCAV playback method, or the like, the maximum operation speed of the system, that is, the maximal processing capacity of signals is specified, and the system is constructed in such a way as the outermost perimeter of the disk is N times the velocity, if the maximum operation speed of the system is N times the velocity. However, in most disks, data is not recorded to the outermost perimeter, and the above speed is a playback criterion, even if the data-recorded area is small, so that there has been a lot of waste. Therefore, in the Japanese Patent Application No. 6-103878, there is proposed a disk playback system that operates in such a way as the criterion of disk playback speed is determined so as to obtain the maximum search speed and high-speed readout, depending on the outermost perimeter of the data-recorded area.
In the above disk playback system, the criterion of the disk speed control is, as mentioned above, the outermost perimeter of the data-recorded area in which data is recorded. Therefore, the playback speed criterion mentioned above is used even if only the data near the inner perimeter of the disk, of the data recorded on the disk, is actually used, or the use frequency of the data at the outer perimeter is very low. Therefore, in the above disk playback system, there has been a problem that the maximum playback speed and maximum search speed that the system owns cannot be effectively used.
An object of the present invention is to provide a disk playback system that effectively uses the maximum playback speed and maximum search speed that the system owns.
The disk playback system stated in claim 1 of the present invention searches for a desired position of a disk on which information data is recorded at a constant linear velocity when received a command from an external device, reads out desired information data from the aforementioned information data, and outputs information data corresponding to the playback format of the aforementioned disk, being characterized in that the playback system is equipped with a determining means that, if the address information of the newest address accessed by an access instruction of the disk is address information indicative of an address outer than the outermost address that has been accessed, renews stored address information to the address information of the newest address, and determines a criterion for speed control of the disk, based on the newest renewed address information, and a rotation control means that controls the speed of the disk, based on the criterion determined by the determining means.
When a disk is played back in a system whose maximum processing capacity is N times the CLV, and if an approximately inner one half area of the data to be played back has been used, for example, the above determining means determines the speed criterion so as to perform processing at that position, i.e., the outermost track position that has been accessed, at N times the velocity, i.e. the maximum processing capacity. When receiving an access instruction for a further outside perimeter, the determining means determines again the speed criterion. By this means, the maximum search speed and high-speed readout can be obtained, depending on the outermost perimeter of the data-recorded area that has been accessed.
The disk playback system stated in claim 2 of the present invention is characterized in that in the disk playback system of claim 1, the aforementioned rotation control means is a CAV control circuit that rotates the disk at a constant angular velocity (CAV).
When a disk is played back in a system whose maximum processing capacity is N times the velocity (CLV), and if an approximately inner one half area of the disk to be played back has been used, for example, the above determining means determines the speed criterion for the angular velocity of the disk so as to perform processing at that position, i.e., the outermost track position that has been accessed, at N time the velocity, i.e. the maximum processing capacity. At this time, the speed at the innermost perimeter becomes N/1.6 times the velocity, and the criterion speed for readout becomes high. When receiving an access instruction for a further outside perimeter, the determining means determines again the speed criterion. By this means, the maximum search speed and high-speed readout can be obtained, depending on the outermost perimeter of the data-recorded area that has been accessed.
The disk playback system stated in claim 3 of the present invention is characterized in that, in the disk playback system of claim 1, the rotation control means is equipped with a CLV control circuit that rotates the disk at the constant linear velocity (CLV) and a variable clock generating circuit that supplies the CLV control circuit with a comparison clock that varies with the output of the determining means.
When a disk is played back in a system whose maximum processing capacity is N times the velocity, and if an approximately inner one half area of the disk to be played back has been used, for example, the above determining means determines the speed criterion for the linear velocity of the disk so as to be able to perform processing at that position, i.e., the outermost track position that has been accessed, at N times the velocity, i.e. the maximum processing capacity. At this time, N/1.6 becomes the criterion for CLV, and readout speed becomes high. When receiving an access instruction for a further outside perimeter, the determining means determines again the speed criterion. By this means, the maximum search speed and high-speed readout can be obtained, depending on the outermost perimeter of the data-recorded area that has been accessed.
The disk playback system stated in claim 4 according to the present invention searches for a desired position of a disk on which information data is recorded at a constant linear velocity, when received a command from an external device, reads out desired information data from the aforementioned information data, and outputs information data corresponding to the playback format of the disk, being characterized in that the playback system is equipped with a determining means that, if the address information of the newest address accessed by an access instruction of the aforementioned disk is address information indicative of an address outer perimeter than the outermost address that has been accessed, renews stored address information to the address information of the newest address, and determines a criterion for speed control of the disk, based on the newest renewed address information, and also equipped with a first rotation control means that rotates the disk at constant angular velocity (CAV), based on the criterion determined by the determining means, a second rotation control means that rotates the disk at constant linear velocity (CLV), and a switching means that switches the first and second rotation control means.
When a disk is played back in a system whose maximum processing capacity is N times the velocity, and if an approximately inner one half area of the disk to be played back has been used, the above determining means determines a speed criterion for the angular velocity and linear velocity of the disk so as to be able to perform processing at that position, i.e., the outermost track position that has been accessed, at N times the velocity, i.e. the maximum processing capacity. At this time, when the disk is rotated at constant angular velocity (CAV), by using the first rotation control means, the speed at the innermost perimeter becomes N/1.6 times the velocity, and the criterion speed for readout becomes high. When the disk is rotated at constant linear velocity (CLV), using the second rotation control means, N/1.6 becomes the criterion for CLV, and readout speed becomes high. When receiving an access instruction for a further outside perimeter than the stored address, the determining means determines again the speed criterion. By this means, the maximum search speed and high-speed readout can be obtained, depending on the outermost perimeter of the data-recorded area that has been accessed.